The present invention also relates to a shoe manufactured with said sole.
The invention also comprises a method for manufacturing said sole and said shoe.
Soles for shoes which are waterproof and permeable to water vapor have now been known for several years.
In this manner, the soles allow the escape of the water vapor generated by perspiration at the sole of the foot, with an obvious improvement in shoe comfort.
A sole of this type is disclosed for example in U.S. Pat. No. 5,044,096, which relates to a vapor-permeable sole which consists of two layer-like portions, respectively an upper portion and a lower portion of a sole, which are made of rubber or other synthetic material and are provided with through holes, and consists in interposing between them a membrane which is impermeable to water and permeable to water vapor and is joined hermetically at its perimeter to the two portions so as to not allow water infiltrations.
Other solutions proposed by the Inventor of record of U.S. Pat. No. 5,044,096 and derived from the use of a vapor-permeable and waterproof membrane inside a sole with a perforated tread are disclosed in subsequent patents.
For example, WO97/14326 discloses a method for manufacturing a shoe which provides a waterproof and vapor-permeable sole which is injected directly onto an upper which is preassembled on a last for molding by direct injection.
The manufacture of the shoe entails injecting into a first mold the lower portion of perforated tread (the portion of the tread that goes into direct contact with the ground).
Subsequently, from the bottom upwardly, the lower tread element that has just been formed, a protective layer arranged so as to be superimposed on the region where the tread holes are formed, a vapor-permeable and waterproof membrane, and finally a vapor-permeable or perforated filler layer, are inserted in a second mold.
The second mold is closed so that the insole of the upper that is preassembled on the last compresses the three layer-like elements described above against the lower tread element.
A second portion of tread is then injected, surrounds said layer-like elements and is joined monolithically to the lower tread element; said second tread portion further forms, on said layer-like elements, a perimetric seal which avoids the rise of liquids.
This manufacturing method therefore entails two separate molds with two steps for preparing them.
The document WO97/14326 discloses a second embodiment.
In this case, the shoe comprises a waterproof and vapor-permeable sole which is directly injected onto an upper which is preassembled on a last for direct injection molding.
The manufacture provides for inserting into the mold a pack which is constituted, from the bottom upwardly, by a protective layer, by a vapor-permeable and waterproof membrane, and by a filler layer.
The mold is closed so that the insole of the preassembled upper compresses the three components of the pack towards the bottom of the mold cavity, on which there are small pins which provide the holes of the tread.
By injecting the material of the tread into a mold, a sole is formed which couples rigidly to the upper and incorporates internally the pack, in practice sealing the membrane perimetrically and thus preventing the rise of liquids outside its edges.
In this embodiment, the injected polymeric material may attack the protective layer, passing through it, with consequent risk of damaging the membrane or of inhibiting its vapor permeability.